Blotto Skorzany fucked around with this message at 00:14 on Dec 22, 2009

Mario Incandenza fucked around with this message at 13:11 on Jan 6, 2010

open my $in, '<', 'in.txt' or die $!;     #open for reading; note error handling;
                                          #$! is analagous to strerror(errno) in C
for my $line (<$in>) {                    #read line at a time
                 #do stuff
}
open(my $out, '>', 'out.txt') or die $!;  #writing; note optional parens for clarity
print $out $stuff_to_output;              #write to output file

use File::Slurp;
my $whole_file = read_file('in.txt');  #note file::slurp handles errors for you, dying on error by default
#do stuff
write_file('out.txt', $output);        #write_file() can also take array or arrayref as second arg

#invoke as ./your_program.pl input_file_1 input_file_2...
open my $out, '>', 'out.txt' or die $!;
while (<>) {                            #diamond operator without arg takes command line arguments
                                        #as input files and scans over them in order line by line;
                                        #if no command line args are present, it reads from stdin
                                        #this can be Very Useful
    #do stuff, noting $_ holds contents of current line
}
print $out $stuff_to_output;

Blotto Skorzany fucked around with this message at 20:28 on Jan 7, 2010

if statement:                                  result:
if(($i=3) .. ($i=6))                           6 repeating    
if(($i>3) .. ($i=6))                           6 repeating
if(($i<3) .. ($i=6))                           6
if(($i=3) .. ($i<6))                           3 repeating
if(($i=3) .. ($i>6))                           3456 repeating
if(($i<3) .. ($i>6))                           1234567
if(($i>3) .. ($i>6))                           45678910
if(($i>3) .. ($i<6))                           45678910
if(($i<3) .. ($i<6))                           12

Captain Frigate fucked around with this message at 17:45 on Jan 8, 2010

Captain Frigate fucked around with this message at 18:04 on Jan 8, 2010

chdir "C:\Documents and Setings\user\My Documents\scripts";
open ($outfile, '>', "new.txt")
	or die "no good: $!\n";

$i = 0;

for my $line (<$outfile>){
	if($i<100){
		print $outfile $i;
		$i++;
	}else{
		die "done: $!\n";
	}
}

for ($i = 1; $i <= 100; $i++) {
	print $outfile $i . "\n";
}

Captain Frigate fucked around with this message at 20:43 on Jan 12, 2010

chdir '/path/to/dir' 
    or die "chdir failed: $!";

open my $infile, '<', '/path/to/file' 
    or die "can't open: $!";
print for <$infile>

1. One of Perl's special variables is $.    the current line number of the last filehandle accessed, meaning you don't have to keep track of it manually
2. print, if supplied with no arguments, will default to printing $_ the default variable for most of Perl's builtin functions and the most used of perl's special variables
3. $_ holds the contents of the current element in a for loop if no name is given

chdir 'C:\Documents and Setings\user\My Documents\scripts'
    or die "Couldn't chdir: $!";
open my $infile, '<', 'test.pl'
    or die "Couldn't open: $!";

for (<$infile>) {
    print if $. > 190;
    print $.;
}